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7.
Vlastnosti Entit
• Each Entity can have any combination of
attributes.
• Two entites of the same kind can have different properties
• Multivalue properties are supported (ie. Array)
• this can be used for 1:N and M:N relations
• Each entity can have it’s parrent
• It’s possible to construct hierarchical structures
• Hierarchies are used for automatic partitioning of the database
• Transactions are possible only across Entity Group members

8.
Datastore limitations
• Not using SQL, only GQL (Python) or JDOQL (Java)
• No joins support, not even anything similar
• No database constraints
• No aggregation functions (count, avg, min, max…)
• Maximum of 1000 records from one query. It’s not possible to go over
this limitation using offset, but cursors support is planned.
• Inequality filter on one property only
SELECT * FROM Person WHERE
birth_year >= 1980 AND birth_year <= 2009
SELECT * FROM Person WHERE
birth_year >= 1980 AND height >= 180
• No global transactions - only inside Entity Group
• No ad-hoc query support. Each type of query needs to have it’s own
index configured. SDK does this automatically.